1. Field of the Invention
This invention relates to magnetic recording mediums of the metallic film-built type and a method for fabricating such mediums.
2. Description of the Prior Art
A recent trend toward high recording density of magnetic disks entails wide utility of continuous thin film types of magnetic recording mediums rather than coating types of magnetic recording mediums wherein magnetic powders such as .gamma.-ferrite are dispersed in organic binders. The thin film-built magnetic recoding mediums have a number of advantages in that they have a high coercive force and can be formed very thin by plating and sputtering techniques. Accordingly, studies have been made on such continuous thin film-type magnetic recording mediums and their fabrication.
In particular, magnetic recording mediums of the type using a Co alloy ferromagnetic film formed by sputtering have been extensively made for achieving high density recording. For instance, Japanese Kokai No. 58-77024 describes a magnetic recording medium which is obtained by forming a Cr film on a non-ferromagnetic substrate to form a non-ferromagnetic metal film on which a Co alloy ferromagnetic film is formed by sputtering.
We found that when a magnetic disk having a Co alloy ferromagnetic film formed by the sputtering as set forth above is used for high density recording, the magnetic anisotropy of the Co alloy and particularly, the magnetic anisotropy of the crystals and the direction of orientation of the crystals relative to the recording plane of the magnetic disk greatly influence the magnetic characteristics of the disk, e.g. residual magnetization characteristics along the tracking and radial directions, a squareness ratio and a coercive force.
In these known magnetic recording disks, the magnetic anisotropy and the direction of orientation of crystals of the Co alloy have not been satisfactorily controlled.
For magnetic recording at high density and at high output power and reproduction of magnetic recording signals, the control of the Co alloy with respect to the magnetic anisotropy and the direction of orientation of the crystals is one of problems to solve.